Conventionally, various ways of combusting a fossil liquid fuel in the form of a fuel emulsion formed by mixing it with water are proposed, in view of energy-saving or the like. Such a fuel emulsion includes, for example, an emulsion fuel or the like in which a special emulsifying agent is used that can make a petroleum-series fuel into a highly hydrophilic gel form by adding it to the fuel. Further, as the method of combusting this fuel emulsion, there is, for example, proposed a method wherein an emulsion fuel, in which water that is made cationic is used, is jetted into a hot cathode chamber heated to a high temperature at which water can be decomposed.
Since the fuel emulsion contains water, unlike a usual fossil fuel, it cannot be ignited in the air at normal temperatures by a burner or the like to be combusted completely, and particularly if the fuel emulsion has a high water content, it cannot be ignited in a usual manner. Hitherto, to utilize such a water-containing fuel emulsion as a fuel to be combusted completely, the temperature of the environment for the combustion has to be brought to a temperature as high as about 1,600.degree. C. Accordingly, although the fuel emulsion itself is expected to be used in various applications, its complete combustion can only be realized in limited special environments. Further, it is difficult to keep such a high-temperature environment, for example, in generally operated furnaces, boilers, gas turbines, and the like, because the flow of the steam and the gas removes the heat, and in addition the energy efficiency and economy pose a great problem for its propagation and practical use.
In addition, in recent years, it is required to reduce the emission of CO.sub.2 (carbon dioxide gas) on a global scale, and a fuel combustion system that can secure certain calories resulting from combustion with the emission of CO.sub.2 lowered as much as possible is desired. Because of the admixture of water, the water/fossil fuel mixed emulsion can reduce the quantity of emission of CO.sub.2 more than fossil fuels when combusted, and from this viewpoint as well there is need for a method and an apparatus for combusting a water/fossil fuel mixed emulsion efficiently and economically.